var numone = prompt ('第一个数字','请输入一个数字');
var numtwo = prompt ('第二个数字','请输入一个数字');
var suanfa = prompt ('算法','请输入运算符');
var num;
document.write(numone);
document.write("</br>");
document.write(numtwo);
document.write("</br>");
document.write(suanfa);
document.write("</br>");

if (suanfa=='-'){
	num=numone-numtwo
}
if (suanfa=='*'){
	num=numone*numtwo
}
if (suanfa=='/'){
	num=numone/numtwo
}
document.write(num);





